Display technologies continue to advance and display devices continue to improve in image quality and resolution. Projection display devices include an optical subsystem for displaying images (e.g., still images or video). Such optical subsystems typically include an illumination source (e.g., a high pressure mercury lamp) for generating light to project such images. The illumination source (lamp) is powered (driven) by a lamp driver circuit. Current lamp driver circuits have certain drawbacks, however.
Current lamp driver circuits include a design tradeoff as most display device lamp bulbs are short arc lamps. To increase the useful life of these lamps, small output capacitors are used in lamp driver circuits to drive lamps in order to reduce transient current that is delivered to a lamp from a driver circuit. However, this may require the use of filtering to reduce ripple currents and thus reduce arc jumping and flicker within the lamp. The use of such filtering conflicts with the goal of reducing the size of the lamp driver circuit's output capacitors. Therefore, there is a trade off between reducing ripple current and reducing the size of the lamp driver circuit output capacitors.
Another drawback of current lamp driver circuits is the overall cost of such circuits. Current approaches for implementing lamp driver circuits utilize two active converters, a front end converter, which may be termed a power factor converter, and a back end converter, which converts the power provided by the front end converter to provide direct current (DC) power that is usable for driving a projector lamp.
And yet another drawback of current lamp driver circuits is they typically use an alternating current power supply. A drawback of using an alternating current power supply is a lack of sufficient isolation in the electronic components of a projector and lamp drive circuitry. This can increase the risk of electrocution if a projector is operational or even if it is shut off. Further, in order to provide sufficient isolation may reduce portability for small form factor projectors, may increase cost, and increase component density within a projector, as non-limiting examples.
Some projection systems may use a relatively low-power lamp, allowing a projection system to use a DC power source, which in turn greatly expands the applications for which the projection system can be used while decreasing some safety risks associated with AC powered projectors. However, the DC power source presents challenges in providing a consistent and constant power source, which can steadily power the lamp and produce illumination with a small amount of brightness variation.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.